FOR THE DOUGH:
2 ¼ teaspoons active dry yeast
¾ cup warm water
½ cup sugar
½ cup canola oil
3 large eggs
1 teaspoon table salt
4 cups all-purpose flour
egg wash (1 egg beaten with 1 tablespoon water)
Dissolve the yeast in the water in a large bowl. Stir in 1 teaspoon sugar and let stand until bubbling, 5–10 minutes.
Add the remaining sugar, oil, eggs, and salt to the yeast mixture. Blend in 1½ cups flour. Add enough of the remaining flour, ½ cup at a time, to make a workable dough. Mix to combine.
On a lightly floured surface or in a mixer with a dough hook, knead the dough, adding more flour as needed, until smooth and springy, about 5 minutes in a mixer or 10 minutes by hand.
Place in an oiled bowl, turning to coat. Cover and let rise in a warm spot until nearly double in size, around 1½–2 hours, or cover with plastic wrap and refrigerate overnight.
Punch down the dough. Let stand for 10 minutes.
FOR THE POPPY SEED FILLING:
2 cups poppy seeds
1 cup water
1 cup sugar
½ teaspoon vanilla extract
pinch of salt
In a nut grinder, coffee grinder, or food processor, grind the poppy seeds.
Alternately, seal them in a plastic bag and crush with a rolling pin, or use a mortar and pestle.
Combine poppy seeds, water, sugar, vanilla extract, and salt in a small saucepan and simmer over medium-low heat, stirring frequently, until the mixture thickens, about 10 minutes. Remove from heat and let cool. Store in refrigerator for up to 1 week.
SHAPING THE YEAST DOUGH HAMANTASCHEN:
Line 3–4 large baking sheets with parchment paper or lightly grease.
On a lightly floured surface, roll out the dough 6mm thick. Cut out 10cm rounds. Place a scant tablespoon of filling in the center of each round. Fold one “side” of the circle over the filling. Then fold a second side over so that the two sides form a triangular point, with the second side overlapping the first at the top of the peak. Then fold the third side in and over the other two, forming the final side of the triangle. Dab each corner of the triangle with water, and press ends together hard. Place on the prepared baking sheets, cover, and let rise about 45 minutes.
Preheat oven to 350°F.
Either use a pastry brush to apply the egg wash to the top of the dough or dip the top of each hamantasch into the bowl containing the egg wash. Bake until golden brown, 25–30 minutes. Transfer to a rack and let cool. Wrap and store at room temperature for up to 3 days or freeze for up to 2 months.